<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* 边框和圆角边框的效果 */
        .demo1 {

            display: inline-block;
            margin-right: 150px;
            height: 250px;
            width: 250px;
            background-color: pink;
            border: 2px solid red;
            border-radius: 50%;
        }

        /* 盒子阴影的效果 */
        .demo2 {
            display: inline-block;
            height: 250px;
            width: 250px;
            background-color: rgb(81, 15, 26);

        }

        .demo2:hover {
            box-shadow: 20px 20px 30px -4px rgba(0, 0, 0, .3);
        }

        /* 浮动的盒子会脱离标准流，直接跑到页面左上角 */
        .demo3 {
            float: left;
            width: 200px;
            height: 200px;
            background-color: blue;
        }

        .demo4 {
            width: 200px;
            height: 200px;
            background-color: sandybrown;
        }
    </style>
</head>

<body>
    <div class="demo1"></div>
    <div class="demo2"></div>
    <div class="demo3">浮动的盒子</div>
    <div class="demo4">标准流的盒子</div>
</body>

</html>